1. Field of the Invention
The present invention relates to a dye having a novel structure, a method of producing the dye and an ink containing the dye.
2. Description of the Related Art
As a result of the dramatic development in recording technology in recent years, high quality color recording and image output can now be performed very simply. Specifically, it is becoming more common to use personal computers and input/output apparatuses, such as digital cameras, scanners, inkjet printers, color laser printers and the like. Recording apparatuses that employ an inkjet recording method have quickly become popular, since their raw material cost is low, rapid recording can be achieved, it is less noisy during recording, and color recording can be easily provided. This has resulted in calls for even further development of such apparatuses. Specifically, there is a need for a recording apparatus which can more easily output images and documents having greater detail with images having excellent color reproduction and which can retain this state for a long period of time.
While water-soluble dyes are usually used as coloring materials constituting the inks used for inkjet recording in this case, a recorded image formed from an ink which contains a water-soluble dye normally suffers from the problem of having poor image durability. On the other hand, although inks which use a pigment for the coloring material form recorded images that have excellent durability, light tends to scatter as a result of the pigment particles. Thus, compared with inks using a dye, inks using a pigment have suffered from the separate problem that color reproducibility of the image and transparency of the image have been poor.
To resolve these problems, investigations have been made to enable image formation with satisfactory storage stability while also maintaining the color reproducibility and transparency of the image, by using a water-soluble dye in the ink which has high weatherability against light and oxidizing gases (e.g., NOx, SOx, ozone etc.) in the air. To solve these problems by using yellow dyes especially and to enable image formation with satisfactory storage stability while also maintaining the color reproducibility and transparency of the image, it has been proposed to use a pyridone azo dye as a high color development water-soluble yellow dye (refer to Japanese Patent Application Laid-Open No. 2001-288393).
A dye having a carboxyl group in the ortho position of a diazo component has also been proposed as a dye having excellent weatherfastness (refer to Japanese Patent Application Laid-Open No. 2003-510398). However, when an image is formed using the dye described in this publication as the ink component, the obtained image has the problem that it does not have sufficient weatherfastness, especially ozone resistance. Further, the humidity resistance of the image is also insufficient.
To faithfully reproduce an RGB image, an inkjet printing method has recently been proposed which uses a specifically colored ink, such as red, green or blue ink, which has excellent color developability (refer to Japanese Patent Application Laid-Open No. 2002-363455). Particularly in the green region, to form natural images, such as of greenery or landscapes, or to form an image of a product lit up using artificial light, the color reproduction range must not only be broad, but it is also important to have excellent vividness, sense of transparency and contrast. There is thus a need for a green ink having superior color tone as well as high weatherfastness and humidity resistance.
On the other hand, the following methods have been proposed for producing a 6-hydroxy-2-pyridone-3-carboxylic acid amide compound, which is an important intermediate for a high color development water-soluble yellow dye: condensation of a β-ketoester and malonic acid diamide; or condensation of a β-ketoamide and malonic acid monoamide-monoester (refer to Japanese Patent Application Laid-Open No. S48-044263).
However, these conventional production methods suffer from problems with availability of their raw materials, restrictions on their application scope, and that in many cases their yield is low. Concerning these points, the reaction in which a cyano group is reacted with an alcohol or an alkene in an acid catalyst is known as a “Ritter Reaction” (refer to J. J. Ritter and P. P. Minieri, J. Am. Chem. Soc., 70, 4045 (1948)). However, no examples in which the Ritter reaction was applied to a pyridone compound have, until now, been reported.